// 最基础的二分查找，注意循环条件就行
class Solution {
    public int search(int[] nums, int target) {
        int left = 0, right = nums.length-1, ret = -1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] < target) {
                left = mid+1;
            } else if (nums[mid] > target) {
                right = mid-1;
            } else {
                ret = mid;
                break;
            }
        }
        return ret;
    }
}